Too great travel driving force of a working vehicle having an HST travel circuit and a work circuit, such as a wheel loader, reduces its lifting force of its lifting arm and thus causes the vehicle to have difficulty in lifting its bucket. In addition, when the bucket is thrust into the mound and lifted, tires skid, thereby reducing travel driving force and decreasing workability.
On the other hand, there are apparatuses known in the related art that limit the maximum displacement of a traveling hydraulic motor in correspondence to the discharge pressure of a working hydraulic pump so as to reduce travel driving force (refer to, for example, Patent Reference Literature #1). In the apparatus disclosed in Patent Reference Literature #1, the displacement of the motor is controlled according to a predetermined characteristic in which the maximum displacement of the traveling hydraulic motor gradually decreases with an increase in the discharge pressure of the working hydraulic pump.
Patent Reference Literature 1: Japanese Patent Publication No. 2818474 (FIG. 2)